Cellulose acetate fibers in nonwoven fabrics

Abstract

Staple fibers and filament yarns formed from cellulose esters, such as cellulose acetate, are described herein, along with methods of making the fibers and their use in nonwoven fabrics and articles. The filament yarns and fibers described herein may be coated with at least one finish and, in some cases, may be coated with two or more finishes selected to enhance the properties of the fibers. Staple fibers as described herein may be used to produce nonwoven webs that are strong, soft, absorbent, and biodegradable, and may be used in wet or dry nonwoven articles for a variety personal care, medical, industrial, and commercial applications.

What is claimed is: 
     
         1 . A staple fiber formed from cellulose acetate, wherein said fiber has a denier of about 0.5 to about 2.75 and a crimp frequency of from about 8 to about 22 CPI measured according to ASTM D3937, and wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of not more than about 0.70 measured according to ASTM D3412, wherein said fiber is at least partially coated with a spinning finish and a top-coat finish, wherein said spinning finish is present on said fiber in an amount of at least about 0.5% FOY measured by solvent extraction according to ASTM D2257; wherein said top-coat finish is present on said fiber in an amount of not more than about 0.5% FOY measured by solvent extraction according to ASTM D2257; wherein each of said spinning finish and said top-coat finish have been applied prior to cutting a filament yarn to form said fiber; wherein said fiber has a Y-shaped or round cross-sectional shape, and a length of about 3 to about 75 mm measured according to ASTM D-5103; and wherein said cellulose acetate has a degree of substitution of not more than 2.5; and wherein said staple fiber is soil biodegradable under the ISO 17566 test method. 
     
     
         2 . The staple fiber of  claim 1 , wherein said fiber has a static half-life of not more than about 12 minutes measured according of AATCC 84-2011 and wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of at least about 0.1 measured according to ASTM D3412. 
     
     
         3 . The staple fiber of  claim 1 , wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of at least about 0.1 measured according to ASTM D3412 and wherein said fiber has a surface resistivity, expressed as log R, of not more than about 11 measured according to AATCC TM76-2011. 
     
     
         4 . The staple fiber of  claim 1 , wherein said fiber is a biodegradable fiber, wherein the total amount of all finishes on said fiber is not more than about 1% FOY measured by solvent extraction according to ASTM D2257, and wherein said fiber exhibits at least one of the following biodegradability characteristics (i) through (iii) below—
 (i) a biodegradation of at least 90% within a period of not more than 180 days, measured according to ISO 14855-1 (2012) under industrial composting conditions; 
 (ii) biodegradation of at least 90% within a period of not more than 2 years, measured according to ISO 17556 (2012) under soil compositing conditions; and 
 (iii) biodegradation of at least 90% within a period of not more than 1 year measured according to ISO 14855-1 (2012) under home composting conditions. 
 
     
     
         5 . A nonwoven web comprising the staple fiber of  claim 1 . 
     
     
         6 . A process for producing crimped, coated cellulose acetate staple fibers, said process comprising:
 (a) forming a cellulose acetate filament yarn comprising plurality of individual cellulose acetate filaments, wherein said individual cellulose acetate filaments have a denier per filament in the range of from about 0.5 to about 2.75, wherein said forming includes applying at least one spinning finish to at least a portion of said filament yarn;   (b) crimping at least a portion of said cellulose acetate filament yarn to provide a crimped filament yarn, wherein said crimped filament yarn has an average crimping frequency, measured in at least 5 different locations of said crimped filament yarn, of from about 6 CPI to about 22 CPI measured according to ASTM D3937; and   (c) cutting said crimped filament yarn to form a plurality of crimped cellulose acetate staple fibers having a length of about 3 to about 75 mm measured according to ASTM D-5103,
 wherein the average tenacity of the filaments of said crimped filament yarn is at least 90 percent of the average tenacity of the filaments of said filament yarn prior to said crimping, 
 wherein said staple fibers have a round or Y-shaped cross-section 
 further comprising applying a top-coat finish to at least a portion of said crimped filament yarn prior to said cutting, wherein the total amount of spinning finish is at least 0.5% FOY and the amount of top coat finish is not more than 0.5% FOY measured by solvent extraction according to ASTM D2257. 
   
     
     
         7 . The process of  claim 6 , wherein said staple fibers have a surface resistivity, expressed as Log R measured according to AATCC TM76-2011, of not more than about 11 and a plurality of said fibers exhibits a fiber-to-fiber staple pad coefficient of friction of at least about 0.10 measured according to ASTM D3412. 
     
     
         8 . The process of  claim 6 , wherein said staple fibers are biodegradable fibers, wherein the total amount of finish on said fibers is not more than about 1% FOY measured by solvent extraction according to ASTM D2257, and wherein said fibers exhibit at least one of the following biodegradability characteristics (i) through (iii) below—
 (i) a biodegradation of at least 90% within not more than 180 days, measured according to ISO 14855-1 (2012) under industrial composting conditions; 
 (ii) biodegradation of at least 90% within not more than 2 years, measured according to ISO 17556 (2012) at ambient temperature; and 
 (iii) biodegradation of at least 90% within not more than 1 year measured according to ISO 14855-1 (2012) under industrial composting conditions. 
 
     
     
         9 . Use of a cellulose acetate staple fiber according to  claims 1 to 4  to form a nonwoven web. 
     
     
         10 . Process for producing a nonwoven web comprising the steps
 (a) providing a plurality of cellulose acetate staple fibers according to one of  claims 1 to 4 ,   (b) introducing the staple fibers into an apparatus for forming a dry-laid nonwoven web, and   (c) forming the staple fibers into a nonwoven web in the apparatus.